This invention is concerned with audio-visual systems and methods, particularly of the type employing a motion picture film projector in conjunction with a magnetic tape player.
The prior art is replete with audio-visual systems employing different combinations of visual and audio media, the media being provided separately or integrally. For example, the visual medium may be a motion picture film or slides and the audio medium may be a magnetic tape or a mechanically reproduced disc record. Motion picture films having integral optical or magnetic sound tracks are well known. The integrated audio-visual media are expensive, however, and lack the versatility of separate media.
A vast library of commercial and educational silent motion picture films, much of it contained in endless loop film cartridges, has been established over many years. The desirability of improving or updating that library by providing a suitable audio program accompaniment has long been recognized. Accordingly, it has been proposed to operate a silent motion picture film projector in synchronism with an audio reproducer, such as a magnetic tape player. In order to provide proper synchronization between the projector and the player, it has been proposed to provide a synchronization mark such as an optical cue or a notch adjacent each frame of the film, and also to provide audio cue tones on the sound medium.
The prior art has recognized that the audio and visual media need not move at the same rate throughout a program, and that greater economy, versatility, and entertainment value are possible if the media are "programmed" so as to move at different rates from time to time. For example, the conserve film the film may be stopped during a program so as to project a single frame for a given length of time while the audio portion of the program proceeds. For special effects the film may be advanced at a rate less than (or greater than) the usual free running rate. Nevertheless, the rates of film advancement and audio medium advancement during a program must be predetermined throughout the program if the program is to be reproduced in the same manner time after time and if desired synchronization between audio and visual parts of the program is to be maintained. In the accomplishment of this and other purposes, the art has proposed many types of cueing schemes.
In one prior cueing scheme, cues on the film start the operation of a tape player, and cues on the tape then start and stop the projector. In another, the tape is started by a cue on the film and is stopped by a cue on the tape. In still another scheme, the rate of film advance is controlled by different signals recorded on the tape. In another, the projector is controlled by combinations of coded markings on the film. In yet another scheme, successive cues recorded on the tape control the frame-by-frame advancement of the film at different rates, the film being advanced one frame for each cue on the tape. In addition, a notch provided on the film permits slewing advancement of the film to locate the beginning of a program.
In general, the prior art cueing schemes and the audio-visual systems that employ them suffer from one or more of the following deficiencies: high cost, poor performance, poor reliability, lack of versatility, deterioration of performance and reliability with age, impossibility or impracticality of application to existing silent film libraries, inability to project film in a silient mode if the tape player is absent or malfunctioning, inability to tolerate the loss or improper detection of cues, inability to tolerate the loss of one or more film frames, and problems in programming, editing, splicing, and the like.